The brain plays a critical role in the transition to reproductive senescence. The integrity of the suprachiasmatic nucleus (SCN) is essential in maintaining regular cyclic GnRH/LH release and regular estrous cycles in young animals. The ability of the SCN to relay time-of-day information to GnRH neurons deteriorates as rat's age, and may underlie the disintegration of GnRH/LH surges in aged rats. My long-term objectives are to understand (1) the mechanisms utilized by the SCN to drive the cyclic GnRH neuronal activity that are required for normal LH surges, and (2) how these mechanisms change with age. The findings of this research will deepen our understanding of factors that influence the "menopausal" transitions and will enhance our insights into potential strategies to delay or manipulate this process. [unreadable] [unreadable] [unreadable]